Pancreastatin receptor is coupled to a guanosine triphosphate-binding protein of the G(q/11)alpha family in rat liver membranes.
Pancreastatin (PST), a recently discovered regulatory peptide derived from chromogranin A, has been shown to have a glycogenolytic effect in the hepatocyte that is mediated by increasing intracellular calcium. Our previous studies on pancreastatin signaling suggested that PST receptor is coupled to some G proteins in the plasma membrane of the hepatocyte. The nature of this interaction was investigated using antisera against G(q/11)alpha by different approaches. Indirect evidence of a pertussis toxin (PT)-insensitive G protein of the family of G(q/11)alpha was obtained by measuring high-affinity guanosine triphosphatase (GTPase) activity in soluble rat liver membranes. PST increased GTPase activity in a dose-dependent manner. This effect was only slightly inhibited by PT pretreatment of the membranes, whereas anti-G(q/11)alpha antisera blocked most of the PST-stimulated GTPase activity. The selective association of the PST receptor with this G protein was further studied by the coelution in wheat germ agglutinin semipurification of the receptor and by immunoprecipitation of the G protein-PST receptor complexes using G-protein-specific antisera. A G protein of the family of G(q/11)alpha was found to be associated with the semipurified PST receptor. Moreover, anti-G(q/11)alpha antisera immunoprecipitated most PST-binding activity (95%), bringing down most of the specific G protein, whereas anti-G(il,2)alpha and -G(o,i3)alpha failed to immunoprecipitate the PST-binding activity. Finally, the coupling of the PST receptor with the effector phospholipase C was disrupted by blocking with G(q/11)alpha antisera, suggesting that a G protein of the family of G(q/11)alpha is a signal mediator from PST receptors to phospholipase C activation in rat liver membranes.
Santos-Alvarez
J
J
Departamento de Bioquímica Médica y Biología Molecular, Facultad de Medicina, Unidad de Investigación Hospital Universitario Virgen Macarena, Universidad de Sevilla, Spain.
González-Yanes
C
C
Sánchez-Margalet
V
V
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D053379:Chromogranin A; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D015151:Immunoblotting; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008297:Male; D010187:Pancreatic Hormones / Q000378:metabolism / Q000494:pharmacology; D011233:Precipitin Tests; D051381:Rats; D017208:Rats, Wistar; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D010738:Type C Phospholipases
D000906:Antibodies; D053379:Chromogranin A; D010187:Pancreatic Hormones; D011964:Receptors, Gastrointestinal Hormone; C029438:receptors, pancreatic polypeptide-specific; C050836:pancreastatin; D010738:Type C Phospholipases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins